PVC Pipe Cyclic Design Method

This paper provides the background for a new method in fatigue life calculations for polyvinyl chloride (PVC) pipe developed by Utah State University that is simple to use and is the recommended practice by the PVC pipe association. Design engineers must select an appropriate pipe wall thickness (or DR) that will accommodate both maximum pressure and repeated surge pressure events. Methods for assessing the number of cycles to failure have been developed for PVC pipe over the past 50 years. The AWWA C900-16 standard has a procedure in appendix B for assessing the number of cycles to failure for PVC pipe, which is based off of testing done at Utah State University’s Buried Structures Laboratory in 2004 and additional research prior to that. The current approach requires input of a mean stress and a stress amplitude and typically requires a root finding approach to calculate a number of cycles to failure. Experience has shown that this method can be difficult and time-consuming for most design engineers to use. This paper looks at a new method that will be used as a design standard in North America to calculate fatigue life in PVC pipes subjected to repeated pressure surge events.